1. Field of the Invention
The present invention relates to an image forming device such as a laser printer. More particularly, the invention relates to a degraded toner discharging and new toner replenishing mechanism operable when fog is detected.
2. Description of the Related Art
Image forming devices, such as laser printers, using toner made from a nonmagnetic, single-component material have conventionally been provided with developer cartridges detachably mounted in the image forming device. The developer cartridge includes an accommodating chamber for accommodating toner and a developing chamber having a developing roller for carrying toner.
This type of developer cartridge is mounted in the image forming device such that the developing roller confronts a photosensitive drum. Toner supplied from the accommodating chamber is carried on the developing roller. The toner is brought into contact with the photosensitive drum to develop an electrostatic latent image formed thereon, creating a toner image. The developed toner image is then transferred onto a sheet of paper by a transfer roller, forming an image on the paper.
However, toner supplied from the accommodating chamber to the developing chamber in this type of developing cartridge gradually deteriorates due to friction and the like generated by the developing roller and a supply roller that supplies toner to this developing roller. Allowing this type of toner to remain in the developing chamber for an extended amount of time can lead to a decline in image quality caused by the generation of fog and the like on the paper.
In view of this problem, Japanese unexamined patent application publication No. HEI-11-119531 proposes a process of supplying new toner from the accommodating chamber while simultaneously discharging degraded toner from the developing chamber. In addition, Japanese unexamined patent application publication No. HEI-10-186855 proposes discharging degraded toner from the developing chamber after supplying new toner from the accommodating chamber.
However, if the developing chamber is replenished with new toner while the degraded toner remains therein, the new toner becomes mixed with the degraded toner, inevitably leading to the generation of fog.
In view of the foregoing, it is an object of the present invention to provide an image forming device capable of replacing toner currently in use with unused toner without causing the used and unused toners to mix together for a substantial amount.
It is another object of the present invention to provide an image forming device in which image quality is improved by controlling fog.
To achieve the above and other objects, there is provided an image forming device that includes a photosensitive member, a developing chamber, a developing member, an accommodating chamber, a waste toner accommodating chamber, a supply auger, a discharge auger, and controller. The photosensitive member has a surface on which a latent image is formed. The developing member is housed in the developing chamber and develops the latent image with toner. Waste toner that is deteriorated in quality stays in the developing chamber. The accommodating chamber accommodates toner. The waste toner accommodating chamber accommodates waste toner. The supply auger supplies toner from the accommodating chamber to the developing chamber. The discharge auger discharges toner from the developing chamber into the waste toner accommodating chamber. The controller controls the supply auger and the discharge auger, wherein the controller executes a toner replacing process for driving the discharge auger to discharge waste toner from the developing chamber and for subsequently driving the supply auger to supply toner from the accommodating chamber to the developing chamber.
With this construction, when the controller executes the toner replacing process, the controller first drives the discharge auger to discharge toner that is currently in use from the developing chamber to the waste developer accommodating chamber. After this discharging operation has completed, the controller drives the supply auger to supply unused toner from the accommodating chamber to the developing chamber. Hence, the toner replacing process replaces toner currently in use in the developing chamber with unused toner such that almost none of the used toner is mixed with the unused toner. As a result, it is possible to improve image quality by replacing used toner with unused toner.
It is desirable to use a deterioration detector that detects deterioration in quality of toner. In this case, the controller executes the toner replacing process when the deterioration detector detects the deterioration of toner.
With this construction, the controller executes the toner replacing process based on the deterioration of the toner. Accordingly, deteriorating toner currently being used in the developing chamber is replaced with new, unused toner. Thereby, maintaining good image quality by replacing toner at a precise timing.